Frequency conversion of air compressor of stabilized gas compressor in Yakla gas collection station

Yakea gas gathering station stabilized gas compressor air cooler frequency conversion transformation Chang Xiaohu, He Lei, Yang Gang, Li Baodong (Sinhua Oilfield Company, Sinopec Northwest Oilfield Company, Xinjiang Kuche 842017) Comprehensive condensation of light hydrocarbons The gassing treatment station was completed and put into operation in November 2005. The designed natural gas processing capacity is 260x104m3/d, and the condensate processing capacity is 17x104t/a. The Yakla gas gathering station uses three CFA34 type stables produced by American Cooper Company. The gas compressor unit is designed to have a rated displacement of 490m3/h, a secondary displacement of 750m3/h, and a three-stage displacement of 2000m3/h. The design first-level working pressure is 0.7MPa, the secondary working pressure is 2.3MPa, and the third-stage working pressure 6.7MPa. The compressor adopts three-stage compression, and the cooling method is air-cooled. The compressed natural gas at each level enters the air cooler for cooling. Aiming at the adverse effects caused by the constant speed regulation of the air compressor of the stabilized gas compressor, the frequency conversion of the compressor air cooler was implemented, which effectively solved various problems such as safety hazards, power waste and product yield degradation of the three compressor air coolers. The smooth and efficient operation of the unit is realized, the operation time of the gas treatment device is improved, the electric energy is saved, and the labor intensity of the personnel is reduced. It is recommended that this technology be promoted and applied in similar oilfield enterprises.

1 Introduction The Yakla gas gathering station is located in Kuche County, Xinjiang. It is an important part of the ground construction project of Sinopec Yakla Damao Dam Gas Field. It was officially put into operation in November 2005. Yakla Gas Collecting Station is a comprehensive condensate gas treatment station integrating natural gas processing, condensate stabilization and light hydrocarbon recovery. Designing natural gas processing Yakla gas gathering station currently uses 3 CBA34 produced by American Cooper Company. The type of stabilized gas compressor unit, the function of the compressor unit is to pressurize the light components flashed out in the condensate treatment system and enter the natural gas processing unit for light hydrocarbon recovery. It is an important equipment in natural gas processing and light hydrocarbon recovery systems.

The rated displacement of the designed unit is 490m3/h, the secondary displacement is 750m3/h, the third-stage displacement is 2000m3/h; the design first-stage working pressure is 0.7MPa, the secondary working pressure is 2.3MPa, and the third-stage working pressure is It is 6.7 MPa. The compressor adopts three-stage compression, and the cooling method is air-cooling. The compressed natural gas at each level enters the air cooler for cooling.

2 Problems and countermeasures Due to the fixed speed of the air compressor of the stabilized gas compressor, the air cooler is always operated at rated power and speed regardless of winter and summer. The winter and summer ambient temperature of the area is not considered in the design (lowest -30°C in winter and 50C in summer) The effect on the operation of the air cooler. In the winter, the corresponding insulation measures were taken, but because the air cooler has no frequency conversion control, the following problems still exist during the use: there are safety hazards: in winter, although the louvers on the air cooler are all closed and covered with rubber, there is still stability. Due to the excessive cooling capacity of the gas compressor, the heavy components are concentrated in the tertiary exhaust line, which makes it easy to freeze the exhaust pipe section and the pressure detecting instrument. If the unit does not detect the correct pressure value, it will issue an alarm or even stop automatically. Frequent shutdown will not only affect the life of the unit, but also have a great impact on the safe and stable operation of the unit.

Waste of electrical energy is serious: due to the large temperature difference between day and night in Gobi, the stable compressor is outside, which is greatly affected by the ambient temperature. When the ambient temperature is low, the demand for natural gas heat exchange is less, and the motor speed of the air cooler is fixed, resulting in quite a lot of operation. The energy is lost from the damper and the baffle, causing unnecessary waste of electrical energy.

Decreased product yield: When the ambient temperature is high, a large amount of moisture in the natural gas will not be fully condensed and directly enter the drying unit, resulting in a decrease in the adsorption effect of the molecular sieve which is originally overloaded, thereby affecting the smooth operation of the drying and cryogenic units and reducing Light hydrocarbon, liquefied gas yield. Affected by the ambient temperature, the frequent shutdown of the stabilized gas compressor unit will also cause a large amount of natural gas to be vented, resulting in unnecessary energy waves and equipment operation and energy conservation. E-mail fee and environmental pollution.

According to the current status of the operation of the air compressor of the stabilized gas compressor, the inverter air compressor is modified by frequency conversion for the purpose of reducing power consumption, optimizing motor operation, and ensuring smooth operation of the device. According to the requirements of on-site operation, the air cooler fan adopts automatic control mode for frequency conversion control.

2.1 The frequency conversion transformation idea adopts a single closed-loop control system. The control value corresponding to the optimal operating temperature boundary of the compressed natural gas is the given signal Xs, and the actual temperature value YT of the natural gas is converted into the feedback signal XF by the temperature transmitter. The deviation value AT of the Xs and the feedback signal XF is subjected to a PID operation, and the operation result is output to the inverter. The inverter drives the fan motor to operate at the frequency side according to the operation result, and the process gas temperature is changed by adjusting the air volume. Rt is the external temperature interference. When the temperature is high, the inverter output frequency increases and the motor speed increases. When the temperature is low, the inverter output frequency decreases and the motor speed decreases. The structural principle of the variable frequency speed control system is as shown.

2.2 Frequency conversion system circuit Stabilized gas compressor air cooler motor adopts two kinds of operation modes: “inverter” and “non-inverter”, which realizes “automatic” and “manual” two control modes. If one mode fails, it can be switched to another in time. A mode that reduces unnecessary downtime. Its circuit principle is as shown.

2.3 Implementation of frequency conversion transformation Yakla gas collection station installed inverters for three air compressors of stabilized gas compressors, and introduced the inverter control configuration into the established DCS system. The central control gives control signals according to the environmental temperature changes. By controlling the voltage and frequency of the inverter output to change the motor speed, the fan air volume is automatically adjusted to reduce the cooling capacity of the air cooler, ensuring stable operation of the stabilized gas compressor in winter, reducing power consumption and avoiding downtime caused by shutdown. Natural gas is vented.

3 Implementation effect In August 2012, after the frequency conversion transformation of the air compressor of the stabilized gas compressor, the safety hazard caused by the exhaust pipe section caused by the low temperature in winter and the frozen plugging of the pressure detection were eliminated. The automatic adjustment of the natural gas temperature ensures the smooth operation of the natural gas processing unit.

After adopting frequency conversion control, by February 2013, it has saved electricity and saved electricity by 26,680 yuan. At the same time, the natural gas venting caused by abnormal shutdown is reduced by 15x104m3, which increases the yield of light hydrocarbons and liquefied gas, and significantly reduces labor intensity.

4 Conclusions In response to the adverse effects caused by the constant speed regulation of the air compressor of the steady gas compressor of the Yakla gas gathering station, the inverter air compressor was transformed. Practice has proved that various problems such as safety hazards, power waste and product yield drop of the three compressor air coolers are effectively solved, and the smooth and efficient operation of the unit is realized, the operation time of the gas treatment device is improved, energy is saved, and the power is reduced. The labor intensity of the personnel. It is recommended that this technology be promoted and applied in similar oilfield enterprises.

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